THE PLANT CELL, Vol 5, Issue 6 667-677, Copyright © 1993 by American Society of Plant Biologists
An Arabidopsis Mutant with a Reduced Level of cab140 RNA Is a Result of Cosuppression
J. A. Brusslan, G. A. Karlin-Neumann, L. Huang and E. M. Tobin
Department of Biology, University of California, Los Angeles, California 90024-1606
We analyzed a mutant of Arabidopsis with a severely reduced level of cab140
RNA. This mutant, named lct for low level of cab140 transcript, was
obtained during a selection for phytochrome signal transduction mutants.
The selection was based on reduced expression of the tumor morphology
shoots gene (tms2), an introduced counter-selectable marker under the
control of the cab140 promoter. Expression of the introduced cab140::tms2
gene was also greatly reduced in lct, but surprisingly, expression of other
phytochrome-regulated genes was not comparably affected. Furthermore, the
lct phenotype could not be separated genetically from the T-DNA insert;
thus, we suggest that this phenotype was caused by cosuppression of the
introduced construct and the endogenous cab140 gene, and that the mutation
causing the cosuppression was located on the T-DNA insert. In vitro nuclear
transcription experiments demonstrated that the suppression was occurring
at the level of transcription. We also found that the suppressed cab140
genes were not significantly more methylated than the nonsuppressed cab140
genes.
